Hi Yeping,
Thanks for the update, for the patch LGTM, so ack.
Thanks,
Tao Liu
On Tue, Jul 30, 2024 at 7:40 PM yp z <wonderzyp@xxxxxxxxx> wrote:
>
> Hi Tao,
>
> Thanks for your suggestion, and this method works well as expected.
>
>> Can we make it simpler, since the value we are looking for is the 2nd
>> oprand of tbnz, there must be a ',' after the value.
>>
>> tbnz w2, #0x1f, 0xffff80008001bed0
>>
>> Can we make it like the following? I haven't tested the following code...
>>
>> if ((pos2 = strchr(pos1, '#'))) {
>> pos2 += 1;
>> for (pos1 = pos2; *pos2 != '\0' && *pos2 != ','; pos2++);
>> *pos2 = '\0';
>> thread_shift = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
>> if (errflag) {
>> thread_shift = 0;
>> }
>> break;
>> }
>
>
>
> Thanks.
> Yeping.ZHENG
>
> Tao Liu <ltao@xxxxxxxxxx> 于2024年7月30日周二 08:55写道：
>>
>> Hi Yeping,
>>
>> On Mon, Jul 29, 2024 at 2:20 PM yp z <wonderzyp@xxxxxxxxx> wrote:
>> >
>> > Hi Lianbo and Tao,
>> > Thank you for your suggestions, and I have rewrote a patch in two cases:
>> >
>> > [1] with vmcoreinfo:
>> > + if (kernel_symbol_exists("kasan_enable_current")) {
>> > + min_thread_shift += 1;
>> > + thread_shift = (min_thread_shift < machdep->pageshift) ? machdep->pageshift : min_thread_shift;
>> > + }
>> >
>> This looks fine to me.
>>
>> >> BTW: can you help point out the current issue is with or without the vmcoreinfo? Yeping
>> >
>> > My issue is with vmcoreinfo of "SYMBOL("kasan_enable_current")", and works well with this patch.
>> >
>> > [2] without vmcoreinfo:
>> >>
>> >> What about somehow the disassembly gives us hex values like:
>> >> #0xe? It won't work by then. Any ideas for this?
>> >
>> > In order to use stol() as expected, I have changed the first non-numeric char to '\0':
>> > + if ((pos1 = strstr(buf1, "tbnz"))) {
>> > + if ((pos2 = strchr(pos1, '#'))) {
>> > + pos2 += 1;
>> > + pos1 = pos2;
>> > + while (*pos2 != '\0') {
>> > + if (!((*pos2 >= '0' && *pos2 <= '9')
>> > + || (*pos2 >= 'A' && *pos2 <= 'F')
>> > + || (*pos2 >= 'a' && *pos2 <= 'f'))) {
>>
>> There are 'x' 'X' not covered, it will not work for the "#0xe" case.
>> Can we make it simpler, since the value we are looking for is the 2nd
>> oprand of tbnz, there must be a ',' after the value.
>>
>> tbnz w2, #0x1f, 0xffff80008001bed0
>>
>> Can we make it like the following? I haven't tested the following code...
>>
>> if ((pos2 = strchr(pos1, '#'))) {
>> pos2 += 1;
>> for (pos1 = pos2; *pos2 != '\0' && *pos2 != ','; pos2++);
>> *pos2 = '\0';
>> thread_shift = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
>> if (errflag) {
>> thread_shift = 0;
>> }
>> break;
>> }
>>
>> Thanks,
>> Tao Liu
>>
>> > + *pos2 = '\0';
>> > + break;
>> > + }
>> > + ++pos2;
>> > + }
>> > + thread_shift = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
>> >
>> > Thanks.
>> > Yeping.ZHENG
>> >
>> > lijiang <lijiang@xxxxxxxxxx> 于2024年7月26日周五 17:23写道：
>> >>
>> >> On Fri, Jul 19, 2024 at 6:40 AM Tao Liu <ltao@xxxxxxxxxx> wrote:
>> >>>
>> >>> Hi Lianbo,
>> >>>
>> >>> On Thu, Jul 18, 2024 at 10:50 PM Lianbo Jiang <lijiang@xxxxxxxxxx> wrote:
>> >>> >
>> >>> > On 7/16/24 4:22 PM, Tao Liu wrote:
>> >>> >
>> >>> > > Hi Yeping,
>> >>> > >
>> >>> > > Thanks for the fix.
>> >>> > >
>> >>> > > On Thu, Jul 11, 2024 at 1:38 PM <wonderzyp@xxxxxxxxx> wrote:
>> >>> > >> When using the crash tool to parse the ARM64 dump file with KASAN enabled, I found that using the bt -a command will cause this tool to crash, the following is the backtrace infomation.
>> >>> > >>
>> >>> > >> (gdb) bt
>> >>> > >> #0 0x00005635ac2b166b in arm64_unwind_frame (frame=0x7ffdaf35cb70, bt=0x7ffdaf35d430)
>> >>> > >> at arm64.c:2821
>> >>> > >> #1 arm64_back_trace_cmd (bt=0x7ffdaf35d430) at arm64.c:3306
>> >>> > >> #2 0x00005635ac27b108 in back_trace (bt=bt@entry=0x7ffdaf35d430) at kernel.c:3239
>> >>> > >> #3 0x00005635ac2880ae in cmd_bt () at kernel.c:2863
>> >>> > >> #4 0x00005635ac1f16dc in exec_command () at main.c:893
>> >>> > >> #5 0x00005635ac1f192a in main_loop () at main.c:840
>> >>> > >> #6 0x00005635ac50df81 in captured_main (data=<optimized out>) at main.c:1284
>> >>> > >> #7 gdb_main (args=<optimized out>) at main.c:1313
>> >>> > >> #8 0x00005635ac50e000 in gdb_main_entry (argc=<optimized out>, argv=<optimized out>)
>> >>> > >> at main.c:1338
>> >>> > >> #9 0x00005635ac1ea2a5 in main (argc=5, argv=0x7ffdaf35dde8) at main.c:721
>> >>> > >> Eventually, I found that it was may caused by not setting irq_stack_size properly, and provide this patch to solve it.
>> >>> > >>
>> >>> > > Could you please re-draft your commit message? The original one looks
>> >>> > > informal. E.g:
>> >>> > >
>> >>> > > A segfault issue was observed on KASAN enabled arm64 kernel due to the
>> >>> > > incorrect irq_stack_size, see the following stack trace:
>> >>> > > ...
>> >>> > > The issue was caused by ...., and this patch will fix the issue by ....
>> >>> > >
>> >>> > >> From 34b28aa8c11e77d20adec4f7705a14d239c8a55f Mon Sep 17 00:00:00 2001
>> >>> > >> From: wonderzyp <wonderzyp@xxxxxx>
>> >>> > >> Date: Mon, 8 Jul 2024 20:11:38 +0800
>> >>> > >> Subject: [PATCH 1131/1131] set_arm64_irq_stack_size
>> >>> > >>
>> >>> > >> Signed-off-by: Yeping Zheng <wonderzyp@xxxxxxxxx>
>> >>> > >> ---
>> >>> > >> arm64.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
>> >>> > >> 1 file changed, 47 insertions(+), 2 deletions(-)
>> >>> > >>
>> >>> > >> diff --git a/arm64.c b/arm64.c
>> >>> > >> index b3040d7..39d891b 100644
>> >>> > >> --- a/arm64.c
>> >>> > >> +++ b/arm64.c
>> >>> > >> @@ -93,6 +93,7 @@ static void arm64_calc_VA_BITS(void);
>> >>> > >> static int arm64_is_uvaddr(ulong, struct task_context *);
>> >>> > >> static void arm64_calc_KERNELPACMASK(void);
>> >>> > >> static int arm64_get_vmcoreinfo(unsigned long *vaddr, const char *label, int base);
>> >>> > >> +static ulong arm64_set_irq_stack_size(struct machine_specific *ms);
>> >>> > >>
>> >>> > >> struct kernel_range {
>> >>> > >> unsigned long modules_vaddr, modules_end;
>> >>> > >> @@ -2223,8 +2224,14 @@ arm64_irq_stack_init(void)
>> >>> > >> if (MEMBER_EXISTS("thread_union", "stack")) {
>> >>> > >> if ((sz = MEMBER_SIZE("thread_union", "stack")) > 0)
>> >>> > >> ms->irq_stack_size = sz;
>> >>> > >> - } else
>> >>> > >> - ms->irq_stack_size = ARM64_IRQ_STACK_SIZE;
>> >>> > >> + } else {
>> >>> > >> + ulong res = arm64_set_irq_stack_size(ms);
>> >>> > >> + if (res > 0){
>> >>> > >> + ms->irq_stack_size = res;
>> >>> > >> + } else {
>> >>> > >> + ms->irq_stack_size = ARM64_IRQ_STACK_SIZE;
>> >>> > >> + }
>> >>> > >> + }
>> >>> > >>
>> >>> > >> machdep->flags |= IRQ_STACKS;
>> >>> > >>
>> >>> > >> @@ -4921,6 +4928,44 @@ static void arm64_calc_KERNELPACMASK(void)
>> >>> > >> }
>> >>> > >> }
>> >>> > >>
>> >>> > >> +static ulong arm64_set_irq_stack_size(struct machine_specific *ms)
>> >>> > >> +{
>> >>> > >> + char *string;
>> >>> > >> + int ret;
>> >>> > >> + int KASAN_THREAD_SHIFT = 0;
>> >>> > >> + int MIN_THREAD_SHIFT;
>> >>> > >> + ulong ARM64_PAGE_SHIFT;
>> >>> > >> + ulong THREAD_SHIFT = 0;
>> >>> > >> + ulong THREAD_SIZE;
>> >>> > > I guess the upper case of variable names is not encouraged, though it
>> >>> > > is the variable that comes from kernel config file.
>> >>> > >
>> >>> > >> + if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
>> >>> > >> + if ((ret = get_kernel_config("CONFIG_KASAN_GENERIC", NULL) == IKCONFIG_Y) ||
>> >>> > >> + (ret = get_kernel_config("CONFIG_KASAN_SW_TAGS", NULL) == IKCONFIG_Y)) {
>> >>> > >> + KASAN_THREAD_SHIFT = 1;
>> >>> > >> + }
>> >>> > >> + }
>> >>> > >> + MIN_THREAD_SHIFT = 14 + KASAN_THREAD_SHIFT;
>> >>> > >> +
>> >>> > >> + if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
>> >>> > > Could the if condition be merged with the prior one?
>> >>> > >
>> >>> > >> + if ((ret = get_kernel_config("CONFIG_VMAP_STACK", NULL)) == IKCONFIG_Y){
>> >>> > >> + if ((ret = get_kernel_config("CONFIG_ARM64_PAGE_SHIFT", &string)) ==
>> >>> >
>> >>> > The "CONFIG_ARM64_PAGE_SHIFT " has been removed since kernel v6.9-rc1,
>> >>> > so this can not work on the latest kernel. See:
>> >>> >
>> >>> > d3e5bab923d3 ("arch: simplify architecture specific page size
>> >>> > configuration")
>> >>> >
>> >>> >
>> >>> > In addition, the IKCONFIG is not available in most distributions, it
>> >>> > can not cover this case. There is a similar discussion there:
>> >>> >
>> >>> > https://www.mail-archive.com/devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx/msg00880.html
>> >>> >
>> >>> > Can you try to handle the current issue with a similar solution?
>> >>> >
>> >>> >
>> >>> > >> IKCONFIG_STR){
>> >>> > >> + ARM64_PAGE_SHIFT = atol(string);
>> >>> > >> + }
>> >>> > >> + if (MIN_THREAD_SHIFT < ARM64_PAGE_SHIFT){
>> >>> > >> + THREAD_SHIFT = ARM64_PAGE_SHIFT;
>> >>> > >> + } else {
>> >>> > >> + THREAD_SHIFT = MIN_THREAD_SHIFT;
>> >>> > >> + }
>> >>> > >> + }
>> >>> > >> + }
>> >>> > >> +
>> >>> > >> + if (THREAD_SHIFT == 0) {
>> >>> > >> + return -1;
>> >>> > >> + }
>> >>> > >> +
>> >>> > >> + THREAD_SIZE = ((1UL) << THREAD_SHIFT);
>> >>> > >> + return THREAD_SIZE;
>> >>> > >> +}
>> >>> > > I'm OK with the approach above, since it directly came from the kernel
>> >>> > > source. However I'm not a fan of checking kernel configs, there might
>> >>> > > be kernels which are compiled without CONFIG_IKCONFIG.
>> >>> > >
>> >>> > > Could we add an approach here, to get the value from disassembly when
>> >>> > > CONFIG_IKCONFIG is negative?
>> >>> > >
>> >>> > > kernel source: arch/arm64/kernel/entry.S:
>> >>> > >
>> >>> > > .macro kernel_ventry, el:req, ht:req, regsize:req, label:req
>> >>> > > ....
>> >>> > > add sp, sp, x0 // sp' = sp + x0
>> >>> > > sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
>> >>> > > tbnz x0, #THREAD_SHIFT, 0f <<<<<<<<
>> >>> > >
>> >>> > > $ objdump -d vmlinux
>> >>> > > ...
>> >>> > > ffff800080010800 <vectors>:
>> >>> > > ffff800080010800: d10543ff sub sp, sp, #0x150
>> >>> > > ffff800080010804: 8b2063ff add sp, sp, x0
>> >>> > > ffff800080010808: cb2063e0 sub x0, sp, x0
>> >>> > > ffff80008001080c: 37800080 tbnz w0, #16,
>> >>> > > ffff80008001081c <vectors+0x1c> <<<<<<<<<<
>> >>> > >
>> >>> > > It is easy to get the THREAD_SHIFT value by disassembling the tbnz
>> >>> > > instruction. What do you think @Lianbo Jiang
>> >>> >
>> >>> > This is a good idea, but it still relies on compiler.
>> >>> >
>> >>> > As we discussed, usually I would recommend finding its values via some
>> >>> > kernel symbols.
>> >>>
>> >>> Yeah, but I didn't find a suitable symbol so far... In addition, the
>> >>
>> >>
>> >> It's true. For the KASAN, it is easy to find a suitable symbol, but it's not easy for the PAGESIZE or PAGESHIFT.
>> >>
>> >> Given that I would suggest covering two cases:
>> >> [1] with vmcoreinfo(see mm/kasan/common.c)
>> >> ...
>> >> int min_thread_shift = 14;
>> >> if (kernel_symbol_exists("kasan_enable_current"))
>> >> min_thread_shift += 1;
>> >>
>> >> thread_shift = (min_thread_shift < machdep->pageshift) ? machdep->pageshift : min_thread_shift;
>> >> ...
>> >>
>> >> [2] without vmcoreinfo
>> >> Use Tao's solution(disassemble kernel code)
>> >>
>> >> The first one is better than the second one in case of having vmcoreinfo, If I understand correctly.
>> >> But we still need to cover the above two cases in the crash tools.
>> >>
>> >> BTW: can you help point out the current issue is with or without the vmcoreinfo? Yeping
>> >>
>> >> Thanks
>> >> Lianbo
>> >>
>> >>> above case is a little different here, the tbnz instruction is not
>> >>> generated from C code, it is written in assembly in
>> >>> arch/arm64/kernel/entry.S file. So I guess there would be a lower
>> >>> possibility if tbnz instruction gets replaced or eliminated by the
>> >>> compilers. Anyway, it's OK to me if you don't want to accept the
>> >>> approach.
>> >>>
>> >>> Thanks,
>> >>> Tao Liu
>> >>>
>> >>>
>> >>> >
>> >>> >
>> >>> > Thanks
>> >>> >
>> >>> > Lianbo
>> >>> >
>> >>> > >
>> >>> > > Thanks,
>> >>> > > Tao Liu
>> >>> > >
>> >>> > >> +
>> >>> > >> #endif /* ARM64 */
>> >>> > >>
>> >>> > >>
>> >>> > >> --
>> >>> > >> 2.25.1
>> >>> > >>
>> >>> >
>> >>>
>>
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